The present invention relates to a method for producing stereoscopic images and a device for implementing this method, together with a screen and an image data storage medium to be used in such a method.
Many techniques have been developed to produce images in three dimensions. Methods requiring the wearing of spectacles make it possible to transmit to each eye of the observer the image intended for it. Mention may be made, for example, of anaglyphs, polarised spectacles and liquid crystal spectacles. In projection booths equipped for the use of such methods, all the viewers, whatever their position, see the object at the same angle. It is still impossible to see either side of the filmed object by moving in front of the screen.
A known system with a lens grating enables the viewer to perceive the stereoscopic effect without wearing spectacles or without using a stereoscopic device. Although the grating avoids the need to wear spectacles, it does not lack other disadvantages. Firstly, it must be perfectly adjusted as regards the images formed behind the lens faces, and the viewer must hardly move during observation or else the image and the stereoscopic effect may no longer be seen. The field of view is limited.
Holography makes it possible to reconstruct the view of a volume perfectly but requires the use of coherent light. Moreover, the volume of the objects being shot is limited. Another drawback of this method lies in the fact that it is impossible to project a hologram.
Other methods, such as the 3D Volumetric Display System (H-P PENEL, L""xc3xa8re de la nouvelle Dimension, Science et Vie, 928, 1995, pp. 68-72) and that described in U.S. Pat. No. 5,111,313, enable animated stereoscopic images to be projected on to a screen but require the use of a coherent light source, and the cylindrical shape of the screen limits the size of the images obtained. Moreover, the deviation of the light rays is achieved by the movement of certain mechanical components, which requires a sophisticated electronic control system.
The aim of the present invention is to avoid the disadvantages of the methods and devices of the prior art, and to devise an improved method enabling complete stereoscopic images to be obtained, with horizontal parallax, from objects of any dimensions, particularly in such a way that the viewer is able to move while perceiving the stereoscopic nature of the image produced.
To solve these problems, according to the invention, a method is used for producing stereoscopic images with horizontal parallax comprising:
a first dispersion by diffraction of electromagnetic rays emitted by an object,
the shooting of the object using at least one lens capable of collecting at least part of the said dispersed electromagnetic rays,
a projection of the shot through a screen facility, and
a second dispersion and a scattering, by the screen facility, of electromagnetic rays emitted during the projection, with the formation of stereoscopic images of the object,
the first and second dispersions producing a lateral deviation of corresponding emitted rays. The invention thus exploits the spectral composition of the sources of radiation and uses the unlimited number of wavelengths contained in a spectral range to obtain as many viewing angles of the same object as there are wavelengths. The method according to the invention makes it possible to produce complete stereoscopic images with horizontal parallax and images that may be coloured. It should be noted that the deviation of light rays through optical components is obtained without movement of the said components. It is unnecessary to use either a sophisticated electronic control system or a coherent light source. The invention allows the shooting of animated objects of unlimited size and under ordinary light. The projection on to a screen, even of large dimensions, makes it possible to change at will the size of the stereoscopic image to be produced.
According to one embodiment of the invention, the second dispersion comprises a lateral deviation of the projected rays in the same direction as, or in the opposite direction to, the lateral deviation of the first dispersion. The method according to the invention thus makes it possible to produce an orthoscopic or pseudoscopic stereoscopic image.
According to another embodiment of the invention, the aforesaid projection is carried out by the aforesaid lens. The method thus allows the direct projection, through a screen, of a stereoscopic image of the object to be viewed.
According to an advantageous embodiment of the invention, the method comprises the reception of image data, obtained during the shooting, on at least one data storage medium, allowing the said projection to be performed later. This reception may, for example, be the sensitisation of a silver-based photosensitive medium permitting projection, or else a recording on a storage medium that may, for example, be electronic. In the latter case, it is generally possible to convert the data into digital form: the main advantage conferred by the digital form lies in the data processing, for example to create special effects or synthetic images.
According to yet another embodiment of the invention, the method comprises an adjustment of the spatial separation between the stereoscopic image and the screen facility by inserting in the various steps of the method at least one additional dispersion of rays by diffraction, with additional lateral deviation. The volume of the image may thus be displaced in the forward-backward direction with respect to the screen.
Details and special features of embodiments of the method according to the invention are indicated in the appended claims 1 to 15.
The invention also relates to a device for producing stereoscopic images.
According to one embodiment, this device comprises:
a first diffraction grating providing for a first dispersion of electromagnetic rays emitted by the object with lateral deviation of the said rays,
a lens capable of collecting at least a part of the dispersed electromagnetic rays, and
a screen facility through which the electromagnetic rays coming from the lens undergo a second dispersion with lateral deviation and scattering. Such a device enables the shooting and projection of the stereoscopic image to be performed simultaneously.
According to another embodiment, the device according to the invention comprises:
a first diffraction grating providing for a first dispersion of electromagnetic rays emitted by the object with lateral deviation of the said rays,
at least one lens capable of collecting at least a part of the dispersed electromagnetic rays,
at least one medium for storing image data capable of receiving the electromagnetic rays collected by the lens or lenses, and later of making possible a projection, through at least one projection lens, of image data transmitted by these collected electromagnetic rays, and
a screen facility through which the electromagnetic rays coming from the projection lens or lenses undergo a second dispersion with lateral deviation and scattering. Such a device makes possible the reception of image data on one or more storage media and the subsequent projection on to the screen of the stereoscopic image obtained by the method according to the invention.
Details and special features of embodiments of the device according to the invention are indicated in claims 16 to 27.
The invention also relates to a screen and a storage medium for image data to be used in the method according to the invention.